Continuous flow multiple tank fuel system



Dec. 26, 1950 D. SAMIRAN 2,535,094

con'rmuous FLOW MULTIPLE TANK FUEL SYSTEM Original Filed Aug. 1, 1945 3 Sheets-Sheet 1 1 mwp 5 9 BY 3 e No ZLM M6 HTTOENEYS Dec. 26, 1950 D. SAMIRAN 2,535,094

CONTINUOUS FLOW MULTIPLE TANK FUEL SYSTEM Original Filed Aug. 1, 1945 3 Sheets-Shet 2 Dec. 26, 1950 D. SAMIRAN 2,535,094 CONTINUOUS FLOW MULTIPLE TANK FUEL SYSTEM Original Filed Aug. 1, l945 3 Sheets-Sheet 3 Patented Dec. 26, .1950

UNITED STATES PATENT OFFlCE CONTINUOUS FLOW MULTIPLE TANK FUEL SYSTEM David Samiran, Fort Wayne, Ind.

3 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without payment to me of any royalty thereon.

This invention is a division of my copending application Serial No. 608,348, filed August 1, 1945, which on July 25, 1950, was issued as Patent No. 2,516,150, and relates to aircraft fuel systems.

In modern aircraft, particularly in warcraft, it is current practice to carry the fuel in a series of separate tanks distributed as uniformly as practicable throughout the available space in the craft, this practice being conducive to uniform weight distribution as well as having the advantage that if one tank is punctured. and loses its fuel, the loss will be proportionally less as the number of tanks is greater.

In multiple tank fuel systems as heretofore constructed and arranged, a selector cock has usually been provided with a position for each tank whereby the pilot upon noting that one tank is empty switches the selector to another. This arrangement, however, has the disadvantage that an emergency pump is required which will pump fuel from some assured source while the changeover from one tank to another is being effected, together with a pressure drop sensitive instrument which will start and stop the emergency pump as the pressure situation requires.

One of the objects of the present invention is to provide a multiple tank fuel system in which, by a single setting of a selector cock, the entire contents of a series of fuel tanks will be delivered to the carburetor of an aircraft engine without the slightest interruption in the flow, but still retaining the ability, when conditions warrant, to manually select the tanks one after the other in any order which the circumstances may indicate as desirable.

In long range missions, particularly in long range bombing missions, where maneuverability is not a requirement during light to the obiective but usually becomes highly important upon arrival at the objective, it is current practice to provide a series of externally borne drop tanks, the fuel in which preferably is used first in getting to the objective, whereupon the drop tanks are discarded.

It is therefore another object of this invention to provide a series of drop tanks which may preferably include a right-wing tank, a le t-wing tank, and a belly tank, with means whereby the wing tanks will be emptied uniformly, part out of each tank so as to maintain a balanced condition,

the wing tanks being completely emptied before any fuel is withdrawn from the belly tank.

Another object is to provide suitable signal means to indicate to a pilot when fuel in a tank is getting low, together with means to shut off the signal together with the pump when the said tank is completely empty.

Other objects, advantages, and meritorous features will become apparent as the invention is further described with reference to the drawings, wherein:

Fig. l is a schematic layout of the improved fuel system which is the subject of this invention.

Fig. 2 is an axial section through one of the float-operated valves shown in the closed position and used to'prevent more fuel entering a tank after it is filled to a predetermined level.

Fig. 2a is a fragmentary section showing the valve of Fig. 2 open.

Fig. 3 is a vertical section through the air pressure control valve when closed.

Fig. 3a is a fragmentary section through the valve of Fig. 3 in the open position.

Fig. 4. is a longitudinal vertical section through one of the float-operated valves used in the drop tanks to maintain their fuel in a level condition.

Like reference characters refer to like parts throughout the several views.

Referring now to the drawing, an aircraft engine It carries the usual engine pump I2 which is operatively connected to the engine to be driven thereby and adapted to supply fuel under pressure to the carburetor it or to a like fuel metering device. A main tank 56 is carried within the aircraft as a permanent part thereof, while a right wing tank 25, a left wing tank 22 and a belly tank 24 are carried externally with releasable connections, 25 and 21, for discarding them when they have served their purpose. A selector cook 25 has its common outlet connected by a pipe 28 to the suction side of the engine pump I2.

Pipes 3!) and 3- 5 carry the fuel from the main and drop tanks, respectively, to the several inflow openings of the selector. The handle 36 of the selector has a pointer 33 for indicating when the selector is set at a desired position. Indicia M and D on the face of the selector facilitate the setting for taking fuel from the main and drop tanks, respectively. The pointer may be moved to third or Off position which indicates that all inlets to the selector are closed.

An electrically driven main pump as is provided for taking fuel from the main tank It, the fuel being delivered through the pipe 36 to the position M on the selector 2%, and, when the selector pointer is at M, through the pipe 28 to the carburetor I4. Suitable electric connections are made from the selector position M to the main pump 40.

In order to. cause the drop tanks 25!, 22, and 24 to discharge fuel through the pipe 34 to posi-- tion D on the selector, these tanks are pressurized, the pressure employed being sufficiently high to raise the fuel by way of a branch pipe 44 to the top of, and into the main tank I6, when so desired. A check valve 43 is provided toprevent return flow in pipe 44. A chick valve 45 is spring loaded whereby, with a uniform pressure in the branches 54, 56 and 58, the fuel in the wing tanks 20 and 22 will be transferred to the main tank I6 ahead of the fuel in the belly tank 24. A combined float operated valve-and-switch mechanism 65 is placed in the bottom of each of the drop tanks 20, 22 and 24, the valves being provided to insure that the fuel will move out of each tank through the fuel pipes 44 and GI uniformly, thereby to maintain a balanced condition, and the switches being provided to light a signal light when the drop tanks are nearly empty. A manual switch not shown is provided and used when it is desired to make the switches of the float mechanism ineffective. The combined float operated valve and switch mechanism identified by the numeral 85 in Fig. 1 is shown to a larger scale and in greater detail in Fig. 4 and will be hereinafter more fully described with reference thereto.

As a means for providing the necessary pressure for the drop tanks, the vacuum pump is used. This pump is already part of the standard equipment on aircraft where vacuum operated instruments are employed. The discharge or pressure side of the vacuum pump 48 is connected, through pipe 41, air-oil separator 43, pipe 49, check valve 58, and an air pressure control valve to the air pressure line 52 from which branches 54, 55, and 58 extend to the tops of the drop tanks 29, 22 and 24 respectively. The check valve 55 is biased to prevent return flow to the pump 46. An air pressure control pipe 59 connects the vacuum side of the pump .6 to the air pressure control valve 5|. The air pressure control valve, identified in Fig. l by the numeral EE, is shown in greater detail and to a larger scale in Figs. 3 and 3a, and is hereinafter described with reference ther: to.

The drop tank fuel transfer pipe 44 discharges into the top of the main tank I5 through float valve 66 this float valve being designed to prevent any more fuel entering tank 16 after a predetermined level is reached. The float valve identified in Fig. l by the numeral 66 is shown to a larger scale and in greater detail in Figs. 2 and 2a and will be hereinafter described with reference thereto.

The float valve, identified in Fig. l by the numeral 66, and shown in detail in Figs. 2 and 2a, comprises a housing in two parts, its and I62, with a diaphragm I84 clamped therebetween. The upper part I89 has a flange 95 secured thereto to faoil'tate connection tothe upper side of the tank IS. A hose connection IE3 is s cured to the upper part I30 by a clamp ring 5 to wh ch is slegured to the upp:r housing part I36 by screws The upper housing part I30 has a central hub H4 with an opening II 6 which is in alignment with the opening in the hose connection I68 and connected pressure tight thereto. An annular space I I 8 surrounds the hub I i l and has a series of radial openings I26 connecting the annular space to the outside'of the housing. A valve Washer I22 carried on the upper side of the diaphragm I94 is secured thereto by a cup-shaped member I21; having a small central leakage opening I253. A spring I28 has its lower end seated on a portion of the lower housing part if)?! and its upper end seated in the cup-shaped member I24, whereby the valve washer I22 is maintained on the seat formed by the end of the hub H4.

A chamber I30 formed immediately under the diaphragm Ifi l is adapted to receive fluid under pressure through the small leakage opening I26 whereby the valve washer I22 is maintained on its seat. A float 132 of cork or similar material has attached to the upper side thereof by bolts I3-l a sheet metal member iBS which carries a pair of hinge ears I38 whereby the float may have hinged connection with the housing portion it by means of the hinge pin I40.

A small valve 262 has a groove 33 around its lower end adapttd for engagement with the sheet metal member I36, whereby the valve 32 is maintained in closed position as long as the fioat is in its upper position shown, whereby the chamber I35 builds up pressure through the opening I25, and, being sealed against leakage through the valve I42 therefore maintains the valve washer I22 in its closed position as shown. When, howevir, by reason of fluid being withdrawn from the tank I6 the float I32 drops to a lower position, the small valve I452 will be opened and the chamber I 36 thereby drained, whereupon fluid will flow in through the connection I08 past the valve part 522 and its seat, outward through the annular space II8 and radial openings I29 into the tank it. An adjustable screw stop I44 limits downward travel of the float.

Air pressure control valve, Figs. 3 and 4a, identified in Fig. 1 by the numeral 5I, shown in section and to a larger scale, comprises a valve body I86 with a rear head I82 and a front head I84 s cured thereto by screws I86, a diaphragm I81 and a gasket I88 being clamped under the rear head I82 and front head I84, respectively, by screws I65 thereby making a pressure tight joint between the body and the two heads and dividing the interior of the valve body into three compartments 268, 259, and 2|6. Hose connections I96 and I92 are provided for connecting to the pipes 49 and 52, respectively. A valve head I94 is secured by a small bolt I95 to the diaphragm I81. A spring I98 has the front end acting against the diaphragm I81, the rear end react ng against an internally threaded part 200 which is ad ustable axially by a screw 202. A cap 224 clamps a washer 283 in position, washer 206 being provided as a bearing for the adjusting screw 282. The chamber 208 above the valve head I94 is connected by a passageway ZIIJ to the atmosphere. The chamber 269 is connected to the pressure side of the pump 46 and to the tops of the drop tanks 20, 22 and 24. The valve seat 2! 2 in the bod I88 has a series of openings 233 which are uncovered when the valve head Hit rises from its seat as in Fig. 3a. A pipe connection 2M ada ted for connection to the pipe F9. Fig. 1, connects the vacuum side of the pump 45 to the chamber 2",; for influencing the action of the diaphragm I87. When the valve I94 is closed, as it necessarily is during normal operatio-n, the leftward force in the chamber 209 greatly exceeds the rightward force in that chamber, because, in chamber 289, there is a greater left wall area than right wall area exposed to the same psi pressure. Moreover, the leftward force contributed by the vacuum in chamber 2H5 must be added tothe leftward force 228 is hinged by the pin 230.

accruing from chamber 209. The spring l98 is then proportioned and adjusted so that it exerts a rightward force somewhat less than that necessary to open the valve 89; as long as the pressure in chamber 229 is normal, but, should a leak occur in pipe connection i9il or 592, so that the pressure in chamber 289 would drop below the required value, the spring Hit would v open the valve lat thereby instantly connectthe selector cock may then be set to allow the engine pump E2 to draw the fuel directly from the drop tanks.

The float-controlled valve and switch mechanisms, identified in Fig. l by the numeral 65 and shown in section and to a larger scale in Fig. 4,

are provided with flanges 2l8 by which they are joined to openings in the bottoms of the drop tanks 28, 22 and 24 by bolts not shown. Each valve and switch mechanism has a body 226 having a valve housing 222 secured to upwardly extending posts 22l on its upper side b screws 223, screen covers 225 and 22? being provided through which fuel from the drop tanks must flow to pass through the valve and a switch housing 224 secured to its lower side b screws which do not appear in the view shown.

The midportion of the body 2253 contains the mechanism which provides the necessary interaction between the valve and the switch. The

valve housing 222 has a pair of spaced apart cars 2226 between which a float-operated lever A tub l r arm 232 has one end anchored in the lever 228 while its outer end carries a float 234i. The lower end of the lever 223 is extended laterally at 236 to provide means for operating the valve to opened or closed position as the float rises or falls. A resilient valve disc 238 dies in a saucer-like part 245! and is held in the desired position by a in 242 which passes through openings in the disc and through an opening in the lever extension 236 near its outer end.

A wire washer 24!: between the part Mil and 236 and a cotter pin 2% positioned slightly away from the bottom of the extension 235 permits limited rocking movement of the valve disc 2-38 whereby it may effectively engage the seat 29-3 in the valve housing 222 when the float is in its lower position. A switch-operated trigger 256 is secured to the lever 228 by a screw 252, the trigger having an elongated slot 252 whereby it be adjusted horizontally.

A neck 25% is made integral with the valve housing 222 for receiving the lower ends of the pipes 24, 6! and 6?, Fig. 1, these lower ends being fixed in and made a part of the drop tanks. Washers 258 of soft synthetic rubber or sim lar material alternating with washers 252 of harder material are held in the neck 25% by a snap ring 252. An entire unit 65 may thus be assembled into a drop tank by merely pushing it up from the bottom so that a pipe enters a neck 256, then bolting the flange M8 to the tank.

The switch operat ng mechanism, whereby an electric light is lit when the drop tank is nearly empty and extinguished when it is quite empty comprises a flanged hub member 264 with a diaby the screws 212, a gasket 212 being provided between the member 264 and the bod 22!] to seal against leakage from the valve compartment into the switch compartment.

A central opening in the member 264 is tapered in both directions from the middle as at 214 to freely receive the rockable switch actuating lever 216 which is hinged in the opening b the pin 218. The switch-actuating lever 275 includes a stem 288 which extend upwardly from the body of the lever leaving a shoulder upon which the collar 282 rests, a gasket 224 being placed under the collar to prevent leakage. A spring 286 forces a collar 288, the diaphragm 265, the collar 282 and the gasket L284 together and against the shoulder on the body of the lever 216 whereby leakage along the stem 280 is prevented. The reaction of the upper end of the spring 286 is taken by the nut 295 which is adiustable on the upper threaded end of the stem 286. A jam nut 292 locks the nut 29% in the adjusted position, the upper end 294 of the jam nut 292 is of conical form and engages the depending end of the trigger 258. A switch operating arm 296 depends from the body of the lever 216 and is adapted to engage the operating stem 298 of a switch 32!].

Switch 3539 is of conventional form being of the type which makes electrical contact when the stem 298 is pushed in, and breaks contact when the stem is released. The switch is mounted on an insulating plate 302 which is adjustable horizontall by loosening the screws 304 so that the arm 2% substantially touches the stem 298 when in the closed valve position shown.

A frusto conical spring 305 rests upon a shoulder in the member 254, its upper end bearing against the collar 282 to maintain the actuating lever 215 in the neutral position shown.

Binding posts 396 are connected one to a source of electrical energy and the other grounded to the housin 224 by flexible leads 310, a light 3|2 or other signal being inserted in the circuit.

The operation of the system is as follows:

Assuming all tanks to be filled, the pilot may preferably turn the selector to M and start the en ine l B, the fuel pump 40, and the vacuum pump 46.

Since the tops of the drop tanks 20, 22 and 24 are all connected through conduits 52, 54, 56, 58, 5!, 59, 49, (ii to the pressure side of the vacuum pump 46, the fuel in the drop tanks is pressurized, the pressure being suflicient to cause the fuel to flow through the conduits 61, 61 and M to the top of the main tank l6 through the float valve 65 and into the tank from which it is pumped by the electrically driven pump 40 to the suction side of the engine pump l2, the float valve 66 admitting pressurized fuel from the drop tanks 22, 22 and 24 only so fast as the pump 40 removes fuel from the main tank It and delivers it to the sucicn side of the engine pump l2.

If the main tank l6 should be damaged, or the electrically driven pump 40 should fail to function, the selector may be turned to D, whereupon the pressurized fuel in the drop tanks will be delivered through conduits 61, 6|, 44, 34, and 28 directly to the suction side of the engine pump 52. It is the function of the spring-loaded valve 45 to retain the fuel in the belly tank 24 until after the wing tanks are emptied, and it is the function of the float valve 65 in the two wing tanks 20 and 22 to restrict the fuel outlet most I in the tank in which the fuel is lowest, thereby to cause the two wing tanks to maintain a balanced relation.

When the two wing tanks are nearly empty, the switch operating trigger 250 of the float valve-and-switch mechanism 65, Fig. 4, contact the cone 294 on the left side and lean the switch actuating lever 216 progressively more to the right as the tank becomes more nearly empty, thus closing the switch 30!! of the float mechanism 65 while there is still a small quantity of fuel in the tank and thereby lighting the signal light 366, Fig. 1, indicating to the pilot that the fuel in the wing tanks is almost depleted. The trigger 250 and the cone 294 are so adjusted, with respect to the float 234, that just as the tank becomes quite empty, the trigger 25% passes over center on the cone 294 to the right side of center (see Fig. 4) and the switch 306 is thereby opened and the signal 3l2 thereby extinguished, just as the valve disc 238 is pressed onto the seat to its closed position. At the option of the pilot the two wing tanks 28 and 22 may now be dropped by undoing the connections 25, 27. The mechanism by which the pilot may loosen these connections to drop these tanks forms no part of this invention and is therefore not herein shown.

After the wing tanks are thus emptied and dropped, fuel flows from the belly tank 24 until its float operated valve-switch mechanism 65 lights the warning signal 76 to indicate that the tank is nearly empty, then shuts off the signal and closes the valve when the tank is quite empty. The belly tank 24 may now also be dropped.

Having described my invention, I claim:

1. In a continuous flow fuel system for an aircraft, a main tank, a drop tank, a fuel outlet control means at the outlet of the drop tank through, which the fuel flows from the drop tank tov the main tank, a signal associated with said control means, means in the drop tank operative at a predetermined low level of the fuel in the drop tank to operate said signal, and means operative upon an empty tank condition insaid drop tank to discontinue said signal and close said fuel outlet control means.

2. In a fuel system for an aircraft, a drop tank having an outflow passageway, an electric signal adapted to close said passageway and light said signal, a combined valve and switch mechanism, a float operative at a predetermined low level of the fuel in said tank to close said switch mechanism to operate said signal, and at a lower predetermined level of said fuel to open said switch to discontinue said signal and coincidentally to close said valve.

3. In an aircraft fuel system, a tank having a fuel discharge opening, an electric signal, an electric switch electrically connected to said signal for controlling said signal, a valve in said discharge opening operable to open or closed position for controlling discharge from said fuel discharge opening, a float supported in said tank for operating said valve and said switch to open or closed positions, a switch closing part on said switch, a float operated part on said valve operable into engagement with said switch closing part by movement of said float to a predetermined low level, whereby said switch is operated and said signal is lit, and operable further and into disengagement from said switch closing part to allow said switch to open and disconnect said signal upon movement of said float to the valve closing position.

DAVID SAMIRAN.

CES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Num er Name Date 2,076,454 Foxwell Apr. 6, 1937 2,421,768 Voliazzo June 10, 1947 

